Aqueous printing inks which use a water-dispersible or dissipatable polyester as, for example, a pigment carrier or binder, are known in the art as taught in, for example, U.S. Pat. Nos. 4,883,714; 4,847,316; 4,704,309; and 4,738,785. The polyesters described in these prior art patents require the presence of a poly(ethylene glycol) moiety (the definition of which includes diethylene glycol) as well as a metal sulfonate moiety attached to an aromatic nucleus. Inks containing such a polyester are known to have many desirable properties such as good adhesion to a variety of substrates and a wide viscosity range. Such inks are highly desirable in the art since they are aqueous or water-based and thus can avoid the use of large amounts of organic solvents.
However, because of the wide range of printing conditions and substrates used in the printing industry, a given ink formulation can have ideal properties for some applications and poor properties for other applications. We have found that printing inks prepared using specific polyesters exemplified in the above cited art have good water resistance properties on some substrates (for example, coated paper) but poor water resistance properties on other substrates (e.g., certain metals such as aluminum). There is a need in the art for polyesters which would impart improved water resistance properties to inks for substrates such as aluminum, while concurrently retaining other desirable properties. Also, there is a need in the art for aqueous inks having improved block resistance properties. We have unexpectedly discovered a new class of polyesters which meet the above-described needs of the art.